I'm biased, but I don't think less trustworthy is a fair assessment. I think you can suggest that open source software provides a different trust model than closed source and distributed by Play, but to conclude it's less trustworthy is a real stretch.

The vast majority of software on Google Play is absolute spyware-laden slop. There are turstworthy apps, sure, but they are drops in an ocean. F-Droid’s trustworthy-to-ad-ridden-slop ratio is pretty much definitionally lower than Google’s, by virtue of it being actually curated. That everything on it is libre and they are working hard on reproducible builds just makes it all the better.